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Identifying patients for insulin pump therapy

As insulin pumps become increasingly popular in the management of type 1 diabetes, health professionals need to understand which patients are suitable for the therapy

In this article…

Why insulin pumps are used to manage diabetes

Advantages and disadvantages of using insulin pumps

Care of people who have insulin pump therapy

Author

Gill Morrison is diabetes and continuous subcutaneous insulin infusion specialist nurse; Philip Weston is consultant diabetologist and endocrinologist, both at Royal Liverpool and Broadgreen University Hospitals Trust

Abstract

More people with type I diabetes are switching from multiple daily injections to a continuous subcutaneous insulin infusion (CSII), otherwise known as insulin pump therapy. This article provides an over view of the concept and general principals of CSII.

This article has been double-blind peer reviewed

Figures and tables can be seen in the attached print-friendly PDF file of the complete article in the ‘Files’ section of this page

5 key points

An insulin pump is a computerised, portable, external device, the size of a small pager

The pump is programmed to meet individual requirements, which can be supplemented with bolus insulin doses

Insulin pump therapy can be used by people who experience glycaemic instability despite an optimised insulin regimen and those with a high level of self-care in diabetes management

NICE only supports the use of insulin pump therapy for people who have type 1 diabetes

Continuous subcutaneous insulin infusion (CSII) provides a continuous delivery of rapid-acting insulin, which is programmed into a pump to meet individual requirements and supplemented with bolus doses of insulin as calculated by the user.

The use of insulin pump therapy is governed by National Institute for Health and Clinical Excellence (2008) guidance, which limits it to individuals with type 1 diabetes and highlights the need for specialist teams to initiate and manage CSII. However, as more health professionals are exposed to insulin pump therapy, it is essential they have an understanding of this intensive insulin-management system.

Insulin pumps

An insulin pump is a computerised portable external insulin delivery device that is about the size of a small pager. The pump itself is attached to the user by an infusion set, which is connected to a subcutaneous cannula or via “patch pump technology” and inserted by the user into subcutaneous tissue. Key infusion sites include the: abdomen; upper, outer buttocks; loin areas and the legs (Walsh and Roberts, 2006).

The pump itself can be secured to the user in a variety of ways such as being inserted into a suitable pocket, clipped to a waistband or even tucked into a bra (Walsh and Roberts, 2006).

Insulin delivery

A key difference between multiple daily injections (MDI) and insulin pump therapy is that a CSII does not require any long-acting or intermediate-acting insulin. The pump just requires the use of rapid-acting analogue insulin, such as lispro, glulisine or aspart (Colquitt et al, 2003). Although soluble insulin has been used in insulin pumps, evidence indicates that rapid-acting analogues provide better outcomes with regard to glycosylated haemoglobin (HbA1c) and episodes of hypoglycaemia (Colqitt et al, 2003; Bode et al, 2002).

The pump has a disposable reservoir, which can contain up to 300 units (3ml) of insulin. A plunger slowly and precisely delivers the insulin continually according to a dose-variable, pre-set programme, known as the basal rate. Extra doses of insulin can be given to correct an elevated blood-glucose level or when a rise in glucose is anticipated, for example when the user has consumed carbohydrates. These are known as bolus doses and are delivered in addition to the basal rate by the user, who calculates the dose and manually operates the pump to deliver the insulin.

Insulin delivery via a pump is more precise than MDI but, as with injections, insulin delivered via a pump is still infused into the subcutaneous tissue rather than the portal system as in normal physiology.

Software

Modern pumps have software packages incorporated within them, which can help users make appropriate calculations of bolus doses of insulin, when used correctly. Some pumps can be linked to a continuous glucose monitoring (CGM) sensor, which will pass information about a user’s current blood-glucose level to the pump. These sensors can be inaccurate, however, so it is vital that users test their blood-

glucose level using a fingerprick test before taking action based on the result from the sensor.

Using CGM does not mean users no longer have to make proactive decisions about their diabetes management; the technology is not sophisticated enough to act as a “closed loop” system or artificial pancreas. At present, CGM use is neither supported by NICE guidance nor funded by the NHS, except in exceptional cases.

Patient suitability for CSII

Selecting individuals for CSII can be controversial. Even with modern pumps and intensive education programmes, it is not the treatment choice for everyone. Some of the indications that it may be appropriate are described below, but these are not comprehensive and it is vital that all prospective users are assessed by a multidisciplinary team that is experienced in CSII.

In my clinical practice the initial assessment appointment for CSII can take over two hours. The positive and negative aspects of using a pump are summarised in Box 1.

Positive indications for CSII

Insulin pump therapy can be helpful for people who experience glycaemic instability despite an optimised insulin regimen, and have a high level of self-care in diabetes management. Such circumstances include:

Dawn phenomena -this is caused by the release of a growth hormone between 3am and 9am and requires higher doses of insulin to accommodate it; this can be factored into the user’s basal rate automatically to prevent a dawn rise in glucose;

Complications of diabetes, such as gastroparesis (reduced gastric emptying) and severe neuropathy;

To obtain NHS funding, prospective pump users must meet NICE (2008) criteria, which only support the use of insulin pump therapy for individuals with type 1 diabetes. NICE (2008) also indicates the situations in which this therapy should be withdrawn.

The advantages of CSII

To ensure that prospective pump users can make an informed choice about their diabetes management, it is essential they are aware of both the advantages and disadvantages of treatment options (Department of Health, 2001).

The main benefit of insulin pump therapy is that it is a precision delivery tool. Insulin is delivered as an individualised continuous infusion with extra bolus doses to cover meals and correction doses (Walsh and Roberts, 2006). It gives people with diabetes an opportunity to fully participate in their own self-care because they can make decisions and adjustments about aspects of the regimen on a movement-to-moment basis (NHS Technology Adoption Centre, 2011).

Research supports the use of CSII because it has been shown to reduce the risk of severe hypoglycaemia, and improve glycaemic control and quality of life (Pickup et al, 2002; Bode et al, 1996). Box 2 explains the reasons behind these positive outcomes.

It is well documented that repeated episodes of hypoglycaemia can cause individuals to develop hypoglycaemia unawareness (Morrison and Weston, 2008). Using CSII means they can avoid severe hypoglycaemia, which will encourage the return of the signs and symptoms of low blood glucose (Morrison and Weston, 2008).

Background insulin requirements are tailored to accommodate a user’s actual diurnal variation throughout the day, such as the dawn phenomena, which can be factored into the basal rate to prevent a dawn rise in glucose. The set basal rate can also be adjusted on a short-term basis to accommodate any temporary changes that are needed in insulin requirements such as increased physical activity, infection, stress or menstruation (Walsh and Roberts, 2006). Software built into some pumps can guide users on how much insulin to give in these circumstances.

Once the basal rate is matched to users’ requirements, they can skip or delay meals without fear of a drop in their blood-

glucose level (Walsh and Roberts 2006; Bolderman, 2002). This means they can enjoy complete dietary freedom and flexibility if they are using a pump. The mealtime bolus doses are manipulated so they are delivered to match normal physiology and can fit in with the glucose release of various food types (Walsh and Roberts, 2006). This is useful for individuals with malabsorption problems such as gastroparesis (Sharma et al, 2011).

Users who only achieve a minimal improvement in HbA1c following the initiation of CSII often still feel better than when they used MDI; this is because the glycaemic fluctuations on a pump are reduced (Hirsch et al, 2005). An increased sense of wellbeing leads to an improved quality of life (Chantelau et al, 1997).

Potential problems

Using an automated system does come with potential problems. If the flow of insulin is interrupted for even a short time, the blood-glucose level will start to quickly rise. If the user does not deal with the situation appropriately, the blood-glucose values will continue to rise and ketoacidosis will develop (Bolderman, 2002).

Those who enjoy contact sports or swimming may see attachment to an external device such as a pump as a problem. However, some pumps are waterproof and there are strategies that can allow users to exercise without their pump while maintaining glycaemic control (Walsh and Roberts, 2006).

As the cannula breaks through the natural barrier of the skin, there is risk of infection at the site, particularly as the cannula is usually left in the skin for 2-3 days. In the worst case scenario, if cannulas are not re-sited at appropriate intervals an abscess can develop, which may require surgical drainage (Walsh and Roberts, 2006).

Altered body image can also be an issue for some people who want to use a pump, particularly women who are concerned that it will interrupt the smooth line of clothes (Walsh and Roberts, 2006). Many people also feel worried about sleeping with a pump or relying on the technology to manage their diabetes (Walsh and Roberts, 2006).

In order to reduce these risks, pump users must take full responsibility for the day-to-day management of their diabetes. The expertise of the professional team providing users with support and education is also a factor that will impact on the success of CSII (NICE, 2008).

Conclusion

The number of insulin pump users in the UK is steadily increasing as people with diabetes become more informed. Since the advent of NICE (2008) criteria, pumps in general are more widely available and diabetes health professionals now have more confidence in the management of CSII.

The benefits of CSII are clear: improved glycaemic control; reduced risk of hypoglycaemia; and improved quality of life and wellbeing. However, although it can be helpful in managing diabetes effectively, it is not a suitable treatment for all and it is certainly not a “cure all” for diabetes. Certain core skills must be learnt by both users and health professionals to enable them to develop the necessary knowledge and problem-solving skills for CSII to be successful. The full benefit of pump therapy will only be achieved with careful user selection, adequate education and ongoing support from a knowledgeable, appropriately resourced insulin pump professional team.

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